The present invention relates to a method for winding copper foil on a core tube.
In a conventional method for winding copper foil on a core tube, as shown in FIG. 1, what is called a pressure-sensitive double-sided adhesive coated tape, which is commercially available, with a width of about 30 mm is affixed to one place on the core tube, and an end portion of the copper foil is bonded to the tape, by which splicing work is finished, and thereafter the copper foil is wound while the core tube is rotated, whereby the manufacturing work for a copper foil roll is performed.
After the manufacturing work is finished, the roll-form copper foil is wrapped with a plastic film to prevent the copper foil from being exposed to the outside atmosphere, and then is put into a goods-delivery box to reduce the influence of vibrations and to prevent damage during transportation, whereby the copper foil roll is shipped to a user.
The reason why the pressure-sensitive double-sided adhesive coated tape is used to splice the copper foil being wound to the core tube is as described below. The core tube for copper foil is used as an article repeatedly used between a copper foil manufacturer and a laminator or an etching maker., i.e. PCB shop, who use copper foil. Inevitably, therefore, the copper foil must be spliced easily to the core tube, and moreover must be peeled off and removed easily from the core tube.
However, in the work for winding copper foil, for copper foil with a nominal thickness of 70 xcexcm, a length of 700 m to 1000 m of copper foil is sometimes wound, and for copper foil with a nominal thickness of 18 xcexcm, a length of 2000 m to 3000 m is sometimes wound. Therefore, poor winding accuracy presents various problems.
For example, if the copper foil is wound loosely on the core tube, and the winding tightness of copper foil is nonuniform at the right and left, the copper foil is loosened by vibrations occurring when the copper foil is transported in a vehicle, so that the core tube slips out of place, which poses a problem in that the copper foil cannot be used by the user.
Also, even if the copper foil roll manufactured by winding copper foil with a nominal thickness of 18 xcexcm or smaller on the core tube could be used by the user without trouble, when the spliced condition of the copper foil and core tube is not good, wrinkles sometimes generate in the copper foil in the range of about 100 m from the core tube, which sometimes produces a portion unusable as a copper-clad laminate.
Further, in manufacturing the copper-clad laminate, a continuous laminating process (sometimes referred to as a roll-to-roll process) has been used in which glass cloth reeled out of a glass cloth roll is impregnated with an insulating resin, and the impregnated glass cloth is directly lapped on copper foil reeled out of a copper foil roll and is cured by heating in an oven, by which the copper-clad laminates are manufactured continuously. In this method, the winding accuracy of copper foil roll is a very important factor contributing to improvement in yields.